If you have an attachment to someone or something, you are fond of them or loyal to them.

An attachment is a device that can be fixed onto a machine in order to enable it to do different jobs.

If someone is on attachment to another company, department, or place, they are working there temporarily.

An attachment is an extra document that is added to another document.

In computing, an attachment is a file which is attached separately to a message that you send to someone.